The use of packet data networks to transport voice information is becoming increasingly popular in the United States and around the world. For example, many service providers offer customers telephone and other voice services, where voice information is digitized and transported over data networks. However, different manufacturers of network equipment and different service providers often use different procedures or protocols to establish and provide the voice services.
As an example of different procedures or protocols, voice services are often established using “en bloc dialing” or “overlap dialing.” In en bloc dialing, all addressing information (such as all of the digits in a telephone or directory number) is contained in a single call control signaling message, and no further address information is transmitted in subsequent signaling messages. In overlap dialing, addressing information may be contained in multiple signaling messages. En bloc dialing is also known as “en bloc signaling,” and overlap dialing is also known as “overlap signaling.” Also, addressing information (such as a telephone or directory number) is said to represent a “destination address.”
Overlap dialing may provide several advantages over en bloc dialing. For example, overlap dialing may be better suited for use in countries that use destination addresses having different lengths. Without overlap dialing, devices that make routing decisions in a network would need to support a full network address routing table, which is inefficient and impractical. With overlap dialing, a call may be routed more efficiently (such as by using only the prefix of a dialed telephone number), and another network (such as a public switched telephone network) may complete the routing decisions.
A problem in conventional data networks is that some network components (such as specific makes or types of gateways) do not support overlap dialing. For example, a given gateway that maps voice information from a Time Division Multiplexing (TDM) format to a Voice over Internet Protocol (VoIP) format may support only en bloc dialing. Similar gateways could support either overlap dialing or en bloc dialing depending on provisioning. A call that actually uses overlap signaling may not have the full destination address in its initial message, while a call using en bloc dialing needs to have the full destination address in its initial message. If a call originates at a gateway that uses overlap signaling and terminates at a gateway supporting only en bloc signaling, the call may be rejected as having an “incomplete” or “invalid” destination address. Furthermore, some countries specifically require that their public communication networks use only en bloc signaling or only overlap signaling. This may create problems, for example, when a gateway in an overlap signaling jurisdiction attempts to set up a communication session involving a gateway in an en bloc signaling jurisdiction.
In various prior systems, some sort of “retry” mechanism is invoked if a call fails for this reason. For example, the party that placed the rejected call could be redirected to a human operator for intervention or to a man-machine interface such as an automated attendant. The automated attendant typically prompted the party to redial the entire destination address or provided recorded instructions explaining how the party should hang up and redial the destination address.